Absolute Flux Calibration of STIS MAMA Imaging Modes
Abstract
The absolute flux calibration of STIS MAMA imaging modes is tested by comparison of observed and predicted count rates. As part of this work, we have derived new, wavelength- dependent aperture corrections for MAMA imaging, and have revised the NUVMAMA imaging throughput at short wavelengths. FUV-MAMA imaging modes clearly show a time dependent sensitivity loss that is consistent with the time dependent sensitivity changes seen in G140L spectra. Once this time dependence is taken into account, count rates measured using 1" apertures for FUV 25MAMA, F25LYA, F25ND3, and F25SRF2 observations are within 5% of predictions made using the prelaunch throughput determination. However, FUV F25QTZ observations show a much larger scatter than expected from Poisson statistics. NUV-MAMA imaging modes also appear to be consistent with the time dependence observed for G230L spectra, although this effect is not as large as for the FUV-MAMA. While most NUV-MAMA imaging modes show adequate agreement with the tabulated sensitivity curve, results for the F25CN182 mode are discrepant. We suggest a revision of the short wavelength throughput of the NUV-MAMA imaging modes to fix this problem. This revision brings the results for all NUV imaging modes to within 5% of predictions.
- Publication:
-
Space Telescope STIS Instrument Science Report
- Pub Date:
- January 2003
- Bibcode:
- 2003stis.rept....1P
- Keywords:
-
- Hubble Space Telescope;
- HST;
- Space Telescope Science Institute;
- STIS;
- Space Telescope Imaging Spectrograph